Gravity map of moon offers clues to other planets' formation

A new NASA map of gravity fields on the moon sheds some light about its rough-and-tumble history, and reveals clues about how all terrestrial planets in the solar system formed, including Earth and Mars.

The gravity data is the first scientific findings from the Gravity Recovery and Interior Laboratory mission, or GRAIL, managed by the Jet Propulsion Laboratory.

The twin probes, named Ebb and Flow, captured the most complete geophysical details of the moon to date during their initial flybys from March through May.

Gravitational forces are linked to rock density on planets, so the GRAIL data showed clear details about the moon's tectonic structures, basin rings, crater peaks and other features.

"It really opens a window into the early stages of just what a violent place the surfaces of terrestrial planets were early in their history," GRAIL principal investigator Maria Zuber said.

The moon was battered by asteroids and other objects far more than previously thought, with a smooth inner surface. The crust is thinner than previously thought at about 25 miles deep.

The findings also showed that fractures on the upper crust penetrated deep into the ground, possibly into the moon's mantle, supporting some ideas about the possibility of life on Mars.

"Mars, we believe, might have had an ancient ocean and we're all wondering where it went," Zuber explained.

The deep upper crust fractures on the moon could similarly be present on Mars, and would have provided a pathway for water as surface conditions on the planet became inhospitable.

"If there ever were microbes on the surface, they could have gone very deep within the crust of Mars," Zuber said.

Ebb and Flow have enough fuel for a second moon mapping, which JPL is currently conducting before the probes crash land on the surface.

"We are opening another window in terms of the geophysics," GRAIL project scientist Sami Asmar of JPL said.